DuckCorp Dico

Found one definition

1.                 From The Jargon File (version 4.4.7, 29 Dec 2003):
                   
   
   
                   
                     
   wart
    n.
       A small, crocky feature that sticks out of an otherwise clean design.
       Something conspicuous for localized ugliness, especially a special-case
       exception to a general rule. For example, in some versions of csh(1),
       single quotes literalize every character inside them except !. In ANSI C,
       the ?? syntax used for obtaining ASCII characters in a foreign environment
       is a wart. See also miswart.